First-principles study of polarization in ZnMgO

Abstract

Wurtzite ZnO can be substituted with up to ~30% MgO to form a metastable ZnMgO alloy while still retaining the wurtzite structure. Because this alloy has a larger band gap than pure ZnO, ZnMgO/ZnO quantum wells and superlattices are of interest as candidates for applications in optoelectronic and electronic devices. Here, we report the results of an ab-initio study of the spontaneous polarization of ZnMgO alloys as a function of their composition. We perform calculations of the crystal structure based on density-functional theory in the local-density approximation, and the polarization is calculated using the Berry-phase approach. We decompose the changes in polarization into purely electronic, lattice-displacement mediated, and strain mediated components, and quantify the relative importance of these contributions. We consider both free-stress and epitaxialstrain elastic boundary conditions, and show that our results can be fairly well reproduced by a simple model in which the piezoelectric response of pure ZnO is used to estimate the polarization change of the ZnMgO alloy induced by epitaxial strain.

References in corpus (5)

• Systematic treatment of displacements, strains and electric fields in density-functional perturbation theory
• First-principles studies of ground- and excited-state properties of MgO, ZnO, and CdO polymorphs
• Elasticity and piezoelectricity of zinc oxide crystals, single layers, and possible single-walled nanotubes
• Electronic, Mechanical, and Piezoelectric Properties of ZnO Nanowires
• Polarization, piezoelectric constants and elastic constants of ZnO, MgO and CdO

Cited by in corpus (9)

• Challenges and opportunities of ZnO-related single crystalline heterostructures
• Structural phase transitions and fundamental band gaps of Mg(x)Zn(1-x)O alloys from first principles
• Local structure evolution in polycrystalline Zn${}_{1-x}$Mg${}_x$O ($0\le x\le 0.15$) studied by Raman and by synchrotron x-ray pair distribution analysis
• Synchrotron X-ray study of polycrystalline wurtzite Zn1-xMgxO (0 <= x <= 0.15): Evolution of crystal structure and polarization
• Spin susceptibility and effective mass of two-dimensional electrons in MgxZn1-xO/ZnO heterostructures
• Local structures of polar wurtzites Zn_{1-x}Mg_{x}O studied by Raman and {67}Zn/{25}Mg NMR spectroscopies and by total neutron scattering
• Linear and non-linear optical response of Mg(x)Zn(1-x)O: A Density Functional study
• Precise calibration of Mg concentration in MgxZn1-xO thin films grown on ZnO substrates
• Electronic and vibrational spectroscopy of miscible MgO-ZnO ternary alloys